Troubleshooting help - sudden loss of power

[Roostabunny]

The damage to the plug could very well be the problem. Scare up $1.79 and replace it. Heck, skip the latte and replace all of them. The sudden onset of the problem also points to this.

Rookie question - the gunk might be the result of a mediocre spark not igniting things well and leaving schmutz behind?

Can I pick these up an auto parts place or just cycle shops?

[KEITH KRAUSE]

Looks like #1 plug may be damp with oil? You also say there's white smoke out of the left exhaust.
I think the spark is being compromised by burning oil. Running on "3 1/2" cylinders at best. A fresh plug will probably help, but only to help prove this. It will probably start to foul soon too.
One check you can try...
Warm up the bike fully, running as it is. Then put in a fresh plug while it's still fully warm and test immediately. If it runs much better, at least initially, that's the problem (piston ring, valve guide seal). Don't test a new plug with the motor cold. If it is oil leaking into the combustion chamber, it may immediately foul/semi-foul the fresh plug and your test will not be certain. Oil leaks are usually greater/worse before the motor heats up.
It would be great if it were just a bad plug but a bad plug won't cause white smoke to appear. Oil leaking causes white smoke. Excess fuel (rich) cause dark/black/heavy exhaust.
If you have a compression gauge, that will prove it too.

[chef1366]

Looks like oil to me too.

[Kcwiro]

could be silly...but I am a silly guy to suggest it... ahem... check them rubbers on your bike to carbs and if your sitll usign the stock airbox make sure that the seal on it is good. I had mine pop off on me after a speed bump and it caused me enough grief...being I did not have the tool I needed to get it to go back on... lucky me I found someone with duct tape wrapped that around it and vwala issue patched until I got home and fixed it right =)

Good luck

[Roostabunny]

Looks like #1 plug may be damp with oil? You also say there's white smoke out of the left exhaust.
I think the spark is being compromised by burning oil. Running on "3 1/2" cylinders at best. A fresh plug will probably help, but only to help prove this. It will probably start to foul soon too.
One check you can try...
Warm up the bike fully, running as it is. Then put in a fresh plug while it's still fully warm and test immediately. If it runs much better, at least initially, that's the problem (piston ring, valve guide seal). Don't test a new plug with the motor cold. If it is oil leaking into the combustion chamber, it may immediately foul/semi-foul the fresh plug and your test will not be certain. Oil leaks are usually greater/worse before the motor heats up.
It would be great if it were just a bad plug but a bad plug won't cause white smoke to appear. Oil leaking causes white smoke. Excess fuel (rich) cause dark/black/heavy exhaust.
If you have a compression gauge, that will prove it too.

OK, I don't love trouble, but I love the puzzle of troubleshooting. Meanwhile I'm pretty green as a mechanic and I'm trying to get my newbie head around this at a basic level. Let me see if I'm understanding this...



If I'm burning oil, that means I'm leaking oil into the combustion chamber. You mentioned piston rings and valve guide seals because those are both parts that fail, thereby allowing oil into the combustion chamber?


Checking the plug will allow me to determine if it's the cracked insulator or oil fouling that's causing my problem.

1. If it's the plug, it won't foul again, and we blame my mediocre photo.
2. If it improves with the new plug, but then fouls again, I'm burning oil and there's a whole troubleshooting sequence for that.

Is that right?

Can you tell I'm scared of burning oil? I didn't even ask what else that fits the scenario could make the plug black.

[bwringer]

Can I pick these up an auto parts place or just cycle shops?

You can get NGK plugs at many auto parts stores -- Advance Auto, Pep Boys, and Napa all carry B8-ES plugs a lot cheaper than bike shoppes. About $1.79 - $1.89 each is normal US pricing.

Autozone does NOT carry NGK plugs.

[Roostabunny]

You can get NGK plugs at many auto parts stores -- Advance Auto, Pep Boys, and Napa all carry B8-ES plugs a lot cheaper than bike shoppes. About $1.79 - $1.89 each is normal US pricing.

Autozone does NOT carry NGK plugs.

Beat you to it. Called this morning, and just got back from Carquest with 4 x shiny new B8ES's. Gotta unthread that terminal on the wire end right? My old plugs just have exposed threads on the tip. I did not shop around due to my normal something-wrong-with-my-bike anxiousness 8-[, and as a result paid a whopping $2.08 apiece.

As an aside, the gap was spot-on right out of the box. Somewhere between .64mm and .76mm. I meant to bring my spark plug socket so I could test on the way home (and post a better pic of that plug), but I forgot it.

BTW, Keith, you said white smoke would indicate oil burning, and I never mentioned that I only got that when I'm warming up. Course, you also said oil burning problems are more pronounced when the engine's cold, so I may have just proved your point, but I thought it worth mentioning that the exhaust is "clean" once she warms up.

[Roostabunny]

Looks dryer than this in real life. I'm not sayin' it's not oil Here's a better pic.

By the way, this plug is a BP7ES, not sure why it's a different plug. Off hand the only difference I see is that there's more of the insulator showing beyond the threads than on the stock ones I just bought.

I swapped the plug and rode 4-5 miles and it felt the same as before. Actually, I'm not quite sure it felt the same, but it definately sounded the same. Might have pulled a little harder, but still not right.

Checked the new plug after getting home and it looked clean and shiny. That might just mean I didn't ride long enough, but let me know what you think.

[KEITH KRAUSE]

Looks dryer than this in real life - not sayin' it's not oil, but here's a better pic. BTW this is a BP7ES, not sure why it's a different plug.

Swapped the plug, rode 4-5 miles and it felt the same as before. Checked the new plug after getting home and it looked clean.

Someone installed the 7 plug because it's a "hotter" plug. It's a very common/weak attempt at fixing a poor combustion/spark problem.
I know you said it looks drier in person but that sure looks like oil to me.
If ANY oil gets on a plug, the oil acts as an insulator. Oil is a poor conductor. Very little, if any spark can get through to allow decent combustion. If a plug is just wet with gas, the gas will soon evaporate and the plug will be dry. Oil won't dry.
You said the bike ran fine but suddenly started this problem. A plug can take just so much and then start to foul or foul completely. Yes, worn valve seals, etc, generally allow oil to leak into the cylinder much more easily when the motor is cold. You may see white smoke. You also happen to see white smoke out of the left side exhaust. As the motor heats up and the clearances tighten, the oil entering/getting past a bad seal will be less and the problem isn't as bad. Over time it will get worse. A piston rings ability to seal can fail suddenly too. A ring can crack. Again, oil can enter and compression will drop, both causing poor combustion/weak or no spark.
Once in awhile, some people describe "white smoke" but they really are seeing condensation. Condensation can happen on colder start up conditions and it will go away as the motor warms fully. It dissipates into the air much faster than true smoke. I can tell the difference between condensation and oil burning but some can't as easily I guess.
Your plug pic and symptoms fit an oil leak. As you can see, even a new plug didn't give any help. I'm guessing that cylinder is low on compression.

[Roostabunny]

As you can see, even a new plug didn't give any help. I'm guessing that cylinder is low on compression.

So next I borrow a buddy's compression gauge?

As long as I'm borrowing tools, let's assume you're right and this cylinder is low on compression (which I'll verify) - what's next?

[KEITH KRAUSE]

You can also place a fresh plug in the cap, lay the ground electrode (tip) solidly against the head and crank the motor. You should see a good bluish spark.
If you then start the bike and it continues the problem, look at the plug again and retest for spark as above. If it no longer sparks well as before or the spark looks weak/or orange, then obviously the conditions in that cylinder are fouling the plug.

[Roostabunny]

You can also place a fresh plug in the cap, lay the ground electrode (tip) solidly against the head and crank the motor. You should see a good bluish spark.
If you then start the bike and it continues the problem, look at the plug again and retest for spark as above. If it no longer sparks well as before or the spark looks weak/or orange, then obviously the conditions in that cylinder are fouling the plug.

You mean you'll see a change in the spark before you can actually see the oil on the plug? For that matter, does my 4 mile plug count as fresh?

[KEITH KRAUSE]

So next I borrow a buddy's compression gauge?

As long as I'm borrowing tools, let's assume you're right and this cylinder is low on compression (which I'll verify) - what's next?

Yes. As I suggested earlier, get a gauge and check compression at all four cylinders to verify. If you have low compression anywhere, it must be repaired. No attempts at tuning or compensating will help.
Lets see the compression numbers.

[focus frenzy]

hmmmm just a idea here, take the diaphram cap off the #1 carb and see if the return spring is where it is suspose to be or is coiled up on top.
I have seen this a couple times and one of those times the owner and given up and thought that one cylinder was toast and parted out the bike.
(I got the carbs on E-bay and discovered his mistake.

the other time my buddy was pulling his hair out on his Kat as it would not run right, it now runs like a scalded cat.

[Roostabunny]

Yes. As I suggested earlier, get a gauge and check compression at all four cylinders to verify. If you have low compression anywhere, it must be repaired. No attempts at tuning or compensating will help.
Lets see the compression numbers.

Yeah, I'm not thinking there's any shortcut to fixing compression, but I'm actually hinting around for you to tell me which jobs that'll entail. Rings? Am I about to get that opportunity to replace my base gasket?

I'm not jumping to conclusions, and I don't want to waste your time with guessing, but I am dyin' with suspense! :-D

I don't expect and answer on this one, but the main things my brain is fixating on is, how many hours/days the bike will be under the knife (it's my ride to work), how much I'll be out in parts, and can I still ride it while I'm planning the job?